Ballistic-resistant panel including high modulus ultra high molecular weight polyethylene tape

ABSTRACT

A ballistic-resistant panel in which the entire panel or a strike-face portion thereof is formed of a plurality of sheets of high modulus high molecular weight polyethylene tape. The sheets of high modulus polyethylene tape can be in the form of cross-plied laminated layers of tape strips or a woven fabric of tape strips. The strips of UHMWPE tape include a width of at least one inch and a modulus of greater than 1400 grams per denier. The ballistic-resistant panel may include a backing layer of conventional high modulus fibers embedded in resin. A wide variety of adhesives were found acceptable for bonding the cross-plied layers of high modulus polyethylene tape together for forming the ballistic-resistant panels of the present invention.

This application is a Continuation-In-Part of U.S. patent application Ser. No. 11/821,659, filed on Jun. 25, 2007 and entitled “Non-Fibrous High Modulus Ultra High Molecular Weight Polyethylene Tape for Ballistic Applications” and is a Continuation-In-Part of U.S. patent application Ser. No. 11/787,094, filed on Apr. 13, 2007 and entitled “Wide Ultra High Molecular Weight Polyethylene Sheet and Method of Manufacture”, of which the entire contents of said applications are incorporated herein in their entirety by reference thereto.

FIELD OF THE INVENTION

The present invention relates to survivability enhancement and more particularly to a ballistic laminate constructed of a plurality of layers of non-fibrous high modulus ultra high molecular weight polyethylene.

BACKGROUND OF THE INVENTION

Survivability enhancement is a well-known objective for armored vehicles or fixed or mobile armored structures in a combat or other high threat environment. If a high-energy projectile strikes a vehicle, the survivability of the occupants and the vehicle can be compromised by the release of spall, which is a spray of high velocity metallic or ceramic debris into the vehicle's interior. Vehicles, ships, aircraft, or structures in a high threat environment are therefore frequently equipped with a spall liner, which is designed to suppress the spall generated when a projectile penetrates the vehicle's interior.

Spall liners are typically comprised of a compressed panel. The compressed panel usually includes a plurality of layers of high modulus, high tensile strength fabric bonded together by a resinous adhesive. If a projectile penetrates the armor of a vehicle, the spall liner absorbs the force of the projectile, with each separate layer delaminating and absorbing some portion of the force of the projectile and thereby dissipating the energy of the projectile as it advances through the spall liner.

Although many different spall liners have been proposed, further enhancements in spall suppression are highly desirable for increasing survivability of armored vehicles and structures.

SUMMARY OF THE INVENTION

The invention is a ballistic-resistant panel formed of a plurality of sheets of high modulus high molecular weight polyethylene tape. The sheets of high modulus polyethylene tape include tape strips bonded together at their edges by heat and pressure or by thermoplastic adhesive combined with heat and pressure. The strips of UHMWPE (ultra high molecular weight polyethylene) tape include a width of at least one inch and a modulus of greater than 1400 grams per denier. The ballistic-resistant panel may include a backing layer of conventional high modulus fibers embedded in resin. A wide variety of adhesives were found acceptable for bonding the sheets of high modulus polyethylene tape together for forming the ballistic-resistant panels of the present invention.

OBJECTS AND ADVANTAGES

The ballistic-resistant panel formed of UHMWPE (ultra high molecular weight polyethylene) Tensylon tape of the present invention includes several advantages over the prior art, including:

(1) The ballistic resistance is improved over ballistic panels formed entirely of conventional ballistic fibers.

(2) The UHMWPE Tensylon tape of the present invention can be produced at a substantially lower price than conventional ballistic fibers. Significant cost savings are therefore obtained by replacing a portion of the conventional high modulus component with the high modulus UHMWPE tape of the present invention.

(4) Forming the ballistic-resistant panel or the strike-face portion of monolithic UHMWPE tape reduces or eliminates joints or seams, thereby improving the ballistic resistance of the ballistic laminate. The UHMWPE tape is a monolithic product, formed as a single piece without joints or seams. This monolithic non-fibrous structure leads to significant sa s in the production of ballistic laminates as the monolithic structure eliminates stress concentrators that are a significant disadvantage of fibrous UHMWPE.

(4) Forming the strike-face portion of monolithic UHMWPE tape provides structural support to the laminate and reduces delamination after a ballistic event.

(5) The UHMWPE tape of the present invention may be formed into sheets or layers by weaving the wide tapes into a woven structure such as a simple basket weave or by simply butting together the strips of tape edge to edge, or by overlapping the edges slightly, and then pressing with pressure, heat and pressure, or by coating with adhesive and pressing. This is vastly simpler and cheaper than forming a sheet or layer from fibers, which requires many more individual ends or packages and lamination with an adhesive or processing by weaving, knitting, or cross-stitching.

(6) The amount of adhesive required to mold a ballistic laminate with a strike-face according to the present invention is significantly lower than that required for a ballistic laminate formed of conventional ballistic fibers. The smooth surface area of the high modulus tape used in the strike-face portion of the ballistic-resistant panel enables a lower adhesive to UHMWPE ratio than is available with ballistics panels formed from conventional UHMWPE. The effectiveness of conventional ballistic-resistant panels is generally negatively affected by the higher adhesive ratios, as the adhesive portion adds weight to the laminate but does not contribute to the ballistic resistance unless the adhesive is specifically designed to produce controlled delamination.

These and other objects and advantages of the present invention will be better understood by reading the following description along with reference to the drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a production process for laminating UHMWPE tape with adhesive in order to produce layers for forming a ballistic laminate according to the present invention.

FIG. 2 is a schematic representation of a second production process for laminating UHMWPE tape with adhesive for the production of a ballistic laminate according to the present invention.

FIG. 3 is a schematic representation in perspective view of two sheets or layers of adhesive-coated unidirectional non-fibrous UHMWPE tape prior to being fused together with heat and pressure to form a cross-plied laminate for use in the construction of a ballistic laminate according to the present invention.

FIG. 4 is a schematic representation as viewed from the side of two sheets of unidirectional non-fibrous UHMWPE tape prior to being fused together with heat and pressure to form a cross-plied laminate.

FIG. 5 is an illustration depicting the forming of a ballistic-resistant panel with cross-plied sheets of adhesive-coated Tensylon and cross-plied sheets of conventional high modulus fibers embedded in resin.

FIG. 6 is a graph depicting ballistic resistance at various molding temperatures and at two separate molding pressures for 2.0 psf panels having 100% Tensylon tape as the high modulus component.

TABLE OF NOMENCLATURE

The following is a listing of part numbers used in the drawings along with a brief description:

Part Number Description 20 laminator/fuser 22 unwind shaft 24 Tensylon tape 26 second unwind shaft 28 adhesive 30 third unwind shaft 32 fourth unwind shaft 34 silicone release paper 36 nip rolls 38 adhesive coated Tensylon web 40 fusing oven 42 chilled platen 44 adhesive coated unidirectional tape 50 laminator/fuser 52 adhesive coated release roll 54 release liner 60 top sheet of adhesive-coated unitape 62 bottom sheet of adhesive-coated unitape 64 strip of Tensylon unidirectional tape 66 joint areas 68 adhesive layer 70 cross-plied sheet of adhesive-coated Tensylon 72 cross-plied sheet of adhesive-coated Tensylon 74 cross-plied sheet of convention fibers in resin 76 cross-plied sheet of convention fibers in resin

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to ballistic laminates having a plurality of layers of high modulus material, either all or some portion of which layers are constructed of non-fibrous, high modulus, ultra high molecular weight polyethylene tape of the type described in U.S. patent application Ser. No. 11/787,094, filed on Apr. 13, 2007, the contents of which are incorporated herein in their entirety by reference thereto. The non-fibrous, high modulus, UHMWPE tape is produced by Tensylon High Performance Materials, Inc. of Monroe, N.C., and sold under the name TENSYLON®. As used in this application, the term “high modulus” refers to materials having a modulus greater than 1,000 grams per denier (gpd).

In order to form an improved strike-face for a ballistic-resistant panel according to the present invention, adhesive was applied to one side of a plurality of webs of unidirectional UHMWPE tape. The webs of adhesive-coated unitape were bonded into a unidirectional or unitape sheet, sheeted, and then cross-plied with additional sheets of adhesive-coated unitape. The cross-plied sheets were molded by heat and pressure into a ballistic laminate. Several conventional adhesives were tested for their effectiveness in forming a ballistic laminate. The test procedure included the following steps:

-   -   (1) Comparing various adhesives for bonding UHMWPE tape for the         purpose of forming unidirectional material for use in         bidirectional cross ply;     -   (2) Evaluating unidirectional tape lamination capability and         consolidation capability;     -   (3) Forming each adhesive variant into a nominal 2.0 pounds per         square foot (psf) test panel at 150 psi and into a second 2.0         psf panel at 3000 psi; and     -   (4) Testing the resultant test panels for ballistic performance.

In order to test the effectiveness of TENSYLON® non-fibrous, high modulus UHMWPE tape as a high modulus component in ballistic-resistant panels, adhesive was applied to one side of Tensylon 19,000 denier tape, hereinafter “Tensylon tape”. The 19,000 denier Tensylon tape included nominal dimensions of 1.62 inches in width, 0.0025 inch in thickness, and a tensile modulus of at least 1,400 grams per denier (gpd). Some of the adhesives were in the form of adhesive scrims, which were laminated to one side of the Tensylon tape, and others were resinous adhesive dispersed in a solvent, which was coated on a release film and then transferred to one side of the Tensylon tape. Preferably, the Tensylon tape has viscosity-average molecular weight of at least 2,000,000, a width of at least 1.0 inch, a thickness of between 0.0015 and 0.004 inch, a width to thickness ratio of at least 400:1, a denier of 6,000 or greater, and a modulus of greater than 1,400 grams per denier. The production of non-fibrous, high modulus, highly drawn ultra high molecular weight polyethylene Tensylon tape is described in detail in U.S. patent application Ser. No. 11/821,659, filed on Jun. 25, 2007, which has been incorporated herein by reference. The monolithic, ultra high molecular weight polyethylene tape having a width of 1-inch or greater and a modulus of 1,400 grams per denier or greater. The non-fibrous UHMWPE tape is obtained by compression molding ultrahigh molecular weight polyethylene powder at a temperature below its melting point and then calendering and drawing and the resultant compression molded polyolefin at a total draw ratio of at least 100:1. The UHMWPE tape can be produced in weights of 6,000 denier to 90,000 denier. The UHMWPE tape of the present invention minimizes the effect of stress concentrators and thereby allows the tape to be drawn at much higher draw ratios than is possible with fibrous UHMWPE. When used in ballistics panels, the high modulus high molecular weight polyethylene tape of the present invention provides superior ballistic performance by increasing the dissipation of the impact energy of a projectile.

With reference to FIG. 1, there is shown a laminator/fuser 20 for laminating adhesive scrims to the Tensylon tape. The laminator/fuser 20 included an unwind shaft 22 with eight rolls of 1.62-inch wide Tensylon tape 24 assembled thereon. Each roll included independent brake tension controls. A second unwind shaft 26 contained a roll of adhesive 28. A third unwind shaft 30 and forth unwind shaft 32 contained rolls of silicone release paper 34. The Tensylon tape 24, adhesive 28, and silicone release paper 34 were laminated together at nip rolls 36 thereby forming adhesive coated Tensylon web 38 sandwiched between the two silicone release liners 34. The silicone release liners 34 prevented the adhesive coated Tensylon web 38 from sticking to any rollers in the oven during fusing. The adhesive coated Tensylon web 38 was then conveyed through a fusing oven 40 to cure the thermoplastic adhesive. A chilled platen 42 cooled the Tensylon/adhesive laminate 38 as it exited the fusing oven 40. After cooling, the release liners 34 were removed from the Tensylon/adhesive laminated web 38 thereby formed an adhesive-coated roll of unidirectional Tensylon 44 at a nominal width of 13.0 inches. The laminator/fuser operated at a line speed of 10 to 20 feet per minute and with fusing oven 40 temperatures between 230° F. and 260° F.

For those adhesives in the form of a resin suspended in a solvent, the resin was applied to one side of a silicone release sheet. With reference to FIG. 2, there is shown a laminator/fuser 50 in which the adhesive-coated silicone release roll 52 was mounted on an unwind shaft 30 with Tensylon tape 24 on unwind shaft 22. The adhesive-coated silicone release web 52 was then nipped against the 1.62-inch wide Tensylon webs that were butt-jointed together at the nip 36. At the nip the adhesive was transferred to the Tensylon web and the eight 1.62-inch Tensylon webs were fused into one sheet as has been described in U.S. patent application Ser. No. 11/787,094, filed Apr. 13, 2007, the contents of which are incorporated herein in their entirety by reference thereto. The adhesive-coated Tensylon 38 was then conveyed through the remainder of the laminator/fuser 50 and the release liner 54 removed from the 13.0-inch nominal width Tensylon/adhesive-coated web 38.

The specific adhesives tested and significant measured properties are presented in Table 1 below:

TABLE 1 Adhesives Tested for effectiveness in bonding Tensylon tape into a ballistic laminate: Adhesive Chemical Melt Temperatures Measured Coat Code Composition (degrees C.) Weight (gsm) A1 Polyamide 100-115  6.2 B1 Polyolefin 93-105 6.0 C1 Ethylene Vinyl 98-112 4.7 Acetate Copolymer D1 Polyurethane 70-100 16.7 E1 Ethylene Acrylic 88-105 N/A Acid Copolymer F1 Polystyrene Isoprene N/A 6.0 Copolymer G1 Polyamide N/A 5.0 H1 Polyurethane N/A 5.0

The adhesives tested included Polyethylene-PO4401 (A1), Polyethylene-PO4605 (B1), Polyethylene-DO184B (C1), Polyurethane-DO187H (D1), and Polyethylene-DO188Q (E1), which are all available from Spunfab, Ltd. of Cayahoga Falls, Ohio; Kraton D1161P (F1), which is available from Kraton Polymers U.S., LLC of Houston, Tex.; Macromelt 6900 (G1), which is available from Henkel Adhesives of Elgin, Ill.; and Noveon-Estane 5703 (H1), which is available from Lubrizol Advanced Materials, Inc. of Cleveland, Ohio. Adhesives A1 through E1 were applied to the Tensylon tape by the laminator/fuser 20 depicted in FIG. 1. Adhesives F1 through H1, which were dispersed in solvents, were coated on a release film and then transferred to one side of the Tensylon tape.

The adhesive-coated unidirectional Tensylon tape, commonly termed “unitape” and consisting of eight strips of UHMWPE tape fused at their edges to form a wide sheet of monolithic UHMWPE tape, was then cut into 12-inch by 12-inch sheets. FIGS. 3 and 4 depict two sheets 60 and 62 of adhesive-coated unitape consisting of strips of Tensylon UHMWPE tape 64 fused at joint areas 66. The joint areas 66 are depicted for clarity in describing the direction of orientation of the UHMWPE tape in FIG. 3, it should be understood that the UHMWPE tape strips 64 are rendered substantially transparent when bonded as described herein therefore making the joint areas 66 appear homogenous with the sheet. The bonding of non-fibrous, high modulus, ultra high molecular weight polyethylene Tensylon tape is described in detail in U.S. patent application Ser. No, 11/787,094, filed on Apr. 13, 2007, which has been incorporated herein by reference. The wide UHMWPE sheet is produced by process that comprises array an array of overlapping or abutting strips of indeterminate length prepared as just described at a temperature below the melting point of the UHMWPE, generally in a range of between about 120° C. and about 155° C. (depending tension applied to the strips during bonding as described below) at a pressure above about 300 pounds per lineal inch (pH) and under a tension of between about 0.3 grams/denier and about 5 grams/denier. It has been calculated that the pressures utilized in the present invention are above about 17.000 psi and about 85,000 psi at the upper end of the described useful pressures. These pressures are considerably higher than the 14.5-145 psi pressures indicated as useful in the prior art European Patent Publication. Once the overlapping structure has been subjected to the process conditions described herein, the total thickness of the joint is about 0.0032 inches., a total reduction of more than about 35% and the molecules have been intermingled, in this case most probably entangled to provide a joint that exhibits a higher strength than the parent material as well as a higher modulus. The top sheet 60 of adhesive-coated unitape is oriented at 90° with respect to the bottom sheet 62. An adhesive layer 68, shown as a transparent layer of adhesive in FIGS. 3 and 4, is bonded to each sheet 60, 62 in the manner described above. As the adhesive is thermoplastic, the two sheets 60, 62 of adhesive-coated unitape are pressed together with heat and pressure which causes the two sheets to bond together into a cross-plied sheet of Tensylon UHMWPE with the bonded sheets cross-plied in the 0° and 90° direction.

To form a ballistic-resistant panel, cross-plied sheets of adhesive-coated Tensylon were stacked until a stack of cross-plied Tensylon of approximately 2.0 psf (pounds per square foot) was obtained. Several of the nominal 2.0 psf stacks were pressed at a pressure of 150 psi and several at a pressure of 3,000 psi. The press cycle included 30 minutes at a temperature of 250° F. to 260° F. and cooling under full pressure to below 120° F. before release thereby forming ballistic-resistant panels of nominally 2.0 psf a real density.

With reference to FIG. 5, a simplified illustration depicts the forming of the preferred embodiment of a ballistic-resistant panel with cross-plied sheets or laminates of adhesive-coated Tensylon 70 and 72 and cross-plied sheets of conventional high modulus fibers embedded in resin 74 and 76. The cross-plied sheets of adhesive-coated Tensylon 70 and 72 are stacked on top of stacked cross-plied sheets of conventional high modulus fibers 74 and 76 and pressure and heat are applied to bond the sheets into a ballistic-resistant panel. As an example, to form a 2.0 psf ballistic-resistant panel having a 50/50 ratio by weight of Tensylon and conventional fiber, a plurality of sheets of cross-plied conventional fibers embedded in resin are laid down until a weight of approximately 2.0 psf is obtained. Cross-plied sheets of adhesive-coated Tensylon are then stacked on top of the cross-plied sheets of conventional high modulus fibers until a total weight of approximately 2.0 psf was obtained. Heat and pressure are then applied to fuse the cross-plied layers of Tensylon and conventional fibers into a ballistic-resistant panel.

The ballistic-resistant panels were then tested for ballistic resistance. Projectiles of 0.30 caliber FSP (Fragment Simulated Projectile) per MIL-P-46593A were fired at the 2.0 psf test panels to obtain ballistics properties of the panels bonded with the various adhesives. The velocities in fps (feet per second) at which 50% of the projectiles failed to penetrate the target (V₅₀) were determined per MIL-STD-662F. Data for the resultant ballistic-resistant panels formed at 150 psi are shown in Table 2 and data for the resultant ballistic-resistant panels formed at 3,000 psi are shown in Table 3 below:

TABLE 2 Data Results for Ballistic-resistant panels of UHMWPE tape formed with various adhesives at Molding Pressure 150 psi and Ballistic Test Results: Average Adhesive Areal 0.30 Cal Adhesive Weight Adhesive Density FSP V₅₀ Description Adhesive ID (gsm) (wt %) (psf) (fps) A1 Polyamide 5.93 10.4 2.01 1873 A1 Polyamide 3.10 5.7 1.88 1984 C1 Ethylene Vinyl 5.93 10.4 2.03 1957 Acetate Copolymer D1 Polyurethane 15.25 22.9 2.02 1818 E1 Ethylene 5.93 10.4 2.02 1832 Acrylic Acid Copolymer B1 Polyolefin 5.93 10.4 2.01 1937 B1 Polyolefin 3.10 5.7 2.05 1878 F1 Polystyrene- 7.40 12.6 2.01 2057 Isoprene Copolymer F1 Polystyrene- 5.70 10.0 2.07 2124 Isoprene Copolymer Dyneema Polystyrene- — — 1.99 2275 HB2 Isoprene Dyneema Polyurethane — — 2.00 2192 HB25

TABLE 3 Data Results for Ballistic-resistant panels of UHMWPE tape formed with various adhesives at Molding Pressure 3,000 psi and Ballistic Test Results: Average Adhesive Areal 0.30 Cal Adhesive Weight Adhesive Density FSP V₅₀ Description Adhesive ID (gsm) (wt %) (psf) (fps) A1 Polyamide 5.93 10.4 1.94 1915 C1 Ethylene 5.93 10.4 1.96 1963 Vinyl Acetate Copolymer B1 Polyolefin 5.93 10.4 1.96 2014 B1 Polyolefin 3.10 5.7 2.02 1970 F1 Polystyrene- 7.40 12.6 2.03 2242 Isoprene Copolymer F1 Polystyrene- 5.70 10.0 2.02 2136 Isoprene Copolymer Dyneema Polystyrene- — — 2.00 2541 HB2 Isoprene Dyneema Polyurethane — — 2.00 2386 HB25

A summary of the data suggest that the 3000 psi ballistic-resistant panels molded with adhesives A1, B1, and C1 rated slightly higher for ballistic performance than did the 150 psi panels. Adhesives B1 and C1 were essentially equal in performance. The V₅₀ results suggest that all of the test panels were acceptable for ballistic resistance of 0.30 caliber fragment simulated projectiles.

Ballistic-resistant panels were then prepared to test the performance of Tensylon tape versus conventional high modulus fibers. Dyneema HB25 cross-plied fibers embedded in resin, available from DSM Dyneema B. V., Urmond, the Netherlands, were formed into a 2.0-psf panel. A panel formed of 100% HB25 as the high modulus component was used as a control sample or baseline. A nominal 2.0-psf panels was also formed of 100% high modulus Tensylon tape. Various other combinations of Tensylon tape and HB25 were formed into ballistic-resistant panels to test the ballistic resistance of panels with various amounts of Tensylon tape in place of the conventional high modulus component and to also test whether the Tensylon tape was more effective in various configurations, such as 1) alternating sheets of Tensylon tape and conventional high modulus component, 2) Tensylon tape as a strike-face at the front of the ballistic-resistant panel, and 3) Tensylon tape as the backing material with conventional high modulus component forming the strike face, and 4) varying the ratio of Tensylon tape to conventional high modulus component. Several of these variations were molded into panels at 150 psi and 250° F. as shown in Table 4 below, and several molded into panels at 150 psi and 210° F. as shown in Table 5. The ballistic-resistant panels were tested with 0.30 caliber FSP rounds and the V₅₀ results recorded.

Table 4 includes, left to right in columns 1 to 7:1) the high modulus composition, 2) the baseline V₅₀ test result for panels formed of one high modulus component, 3) the V₅₀ test result for panels formed with a Tensylon strike-face, 4) the V₅₀ test result for panels formed with HB25 as the strike-face, 5) the calculated V₅₀, and 6) the delta V₅₀ which is the difference between the calculated V₅₀ and the actual V₅₀ recorded in columns 3, 4, or 5. The calculated V₅₀ is determined by the Rule of Mixtures wherein the property of a composite is proportional to the volume fractions of the materials in the composite, thus the calculated V₅₀ for a 50/50 ratio of Tensylon C and HB25 is V₅₀=0.5(1650)+0.5(2250) or V₅₀(calculated)=1950. The Tensylon C (Ten C) and Tensylon A (Ten A) were panels molded with different levels of polyolefin adhesive. Tensylon A (Ten M included 5.7% by weight of polyolefin adhesive and Tensylon C (Ten C) included 10.4% by weight of polyolefin adhesive.

Thus, if the Delta V₅₀ is within plus or minus 50 fps, the Rule of Mixtures is a good predictor of the final V₅₀ value, and there is no effect from the manner in which the separate high modulus components are combined in the panel. Thus the V₅₀ for alternating layers of Tensylon tape and HB25, which is represented by line 4 of the table, is predicted by the Rule of Mixtures. However, if the absolute value of the Delta V₅₀ is significantly greater than 50 fps for several of the test panels, it implies that the order in which the high modulus components are arranged in the ballistic-resistant panel is statistically significant. Thus, where the Tensylon tape is placed with respect to front or back in the ballistic-resistant panel has a significant effect on the ballistic performance of the panel. A Delta V₅₀ that is greater than +50 fps indicates a higher ballistic resistance result than expected by the Rule of Mixtures and thus an advantageous configuration of high modulus components within the panel. A Delta V₅₀ that is less than −50 fps indicates a lower ballistic resistance result than expected by the Rule of Mixtures and thus an undesirable configuration of high modulus components within the panel.

Therefore, it can be concluded from the test results in Table 4 that the compositions in rows 5 and 10 through 12 are advantageous for producing a panel with high ballistic resistance. Column 1 shows the high modulus composition of these panels are 25% Tensylon/50% HB25/25% Tensylon (panel 5), 25% Tensylon/75% HB25 (panels 10 and 11), and 50% Tensylon/50% HB25 (panel 12). Results therefore show that a strike-face consisting of high modulus UHMWPE Tensylon tape improves the performance of ballistic-resistant panels. In the final ballistic-resistant panel, the adhesive was less than 20 weight percent of the total weight of the panel.

TABLE 4 Test Results of 2.0 psf Ballistic-resistant panels at Molding Pressure 150 psi and 250 ° F. Temperature: High Baseline Tensylon Tensylon Calculated Delta Modulus Ratio 0.30 cal. Front Back V₅₀ V₅₀ Component (%) V₅₀ (fps) V₅₀ (fps) V₅₀ (fps) (fps) (fps) HB25 100 2250 — — — — Tensylon C 100 1650 — — — — Tensylon A 100 1933 — — — — TenC/HB25 50/50 — 1965 — 1950 +15 alt.* TenC/HB25/ 25/50/25 — 2211 — 1950 +261 TenC HB25/TenC/ 25/50/25 — — 1989 1950 +39 HB25 HB25/TenA 50/50 — — 1933 2092 −159 HB25/TenC 50/50 — — 1750 1950 −200 HB25/TenC 75/25 — — 1852 2101 −249 TenC/HB25 25/75 — 2333 — 2101 +232 TenA/HB25 25/75 — 2255 — 2151 +104 TenC/HB25 50/50 — 2217 — 1950 +267 TenC/HB25 alt.* - alternating layers of Tensylon C and HB25.

Table 5 includes ballistic test results for panels of various compositions of Tensylon UHMWPE tape and HB25 fibers molded at 150 psi and 210° F. The ballistic-resistant panels were tested with 0.30 caliber FSP rounds and the V₅₀ velocities recorded.

TABLE 5 Test Results of 2.0 psf Ballistic-resistant panels at Molding Pressure 150 psi and 210 ° F. Temperature: High Baseline Tensylon Tensylon Calculated Delta Modulus Ratio 0.30 cal. Front Back V₅₀ V₅₀ Component (%) V₅₀ (fps) V₅₀ (fps) V₅₀ (fps) (fps) (fps) HB25 100 2154 — — — — Tensylon A 100 1986 — — — — HB25/TenA 50/50 — — 1909 2070 −161 TenA/HB25 50/50 — 2289 — 2070 +219 TenA/HB25 25/75 — 2300 — 2112 +188

As reference to Table 5 shows, the ballistic resistance for the 2.0 psf panels molded at 150 psi and 210° F. was improved significantly with Tensylon UHMWPE tape used as the strike face of the panel. The improvement in ballistic resistance with the addition of Tensylon tape as the strike face therefore occurred with panels molded at 250° F. (Table 4) as well as at 210° F. (Table 5).

Table 6 includes ballistic test results for 3.8 nominal psf ballistic-resistant panels composed of Tensylon UHMWPE tape and aramid fabric molded with SURLYN® resin at 150 psi and 250° F. SURLYN® is an ethylene/methacrylic acid copolymer available from DuPont Packaging and Industrial Polymers of Wilmington, Del. The aramid fabric is produced commercially by Barrday, Inc. under the trade name Barrday Style 1013. The aramid fabric was composed of 3,000 denier Kevlar® 29 in fabrics of 14 oz/yd² weight. One ply of 1.5-mil CAF film (SURLYN® resin) was used between each ply of Tensylon tape. (As a result of aramid fabric and Tensylon tape weight variances, it was difficult to match a real densities. The ballistic-resistant panels were tested with 0.30 caliber FSP rounds and the V₅₀ velocities recorded.

TABLE 6 Test Results of 3.3 psf Ballistic-resistant panels at Molding Pressure 150 psi and 250 ° F. Temperature: Baseline High 0.30 cal. Tensylon Tensylon Calculated Delta Modulus Ratio FSP Front Back V₅₀ V₅₀ Component (%) V₅₀ (fps) V₅₀ (fps) V₅₀ (fps) (fps) (fps) Aramid 100 2491 — — — — Tens/Ara alt.* 50/50 2320 — — 2405 −85 Tens/Ara 50/50 — 2632 — 2405 +227 Ara/Tens 50/50 — — 2275 2405 −130 Tens/Ara alt.* - alternating layers of Tensylon and Aramid.

As shown in Table 6, the test panel with a Tensylon tape strike face had ballistic resistance of 2632 fps, which was significantly higher than that predicted by the Rule of Mixtures.

Table 7 includes ballistic test results for 3.8 nominal psf ballistic-resistant panels composed of Tensylon UHMWPE tape and HB25 and tested with an NIJ Level III M80 ball projectile (U.S. military designation for 7.62 mm full metal jacketed bullet).

TABLE 7 Test Results - 3.8 psf Ballistic-resistant panels, M80 Ball: High Molding Areal Calculated V₅₀ Delta Modulus Ratio Pressure Density M80 ball M80 ball V₅₀ Component (%) (psi) (psf) V₅₀ (fps) (fps) (fps) HB25 100 150 4.01 — 2965 — Tensylon 100 150 4.00 — 2107 — Tens/HB25 alt.* 50/50 150 3.80 2565 2416 −149 Tensylon/HB25 50/50 150 3.85 2565 2880 +315 Tensylon/HB25 25/75 150 3.85 2750 2897 +147 Tens/HB25 alt.* - alternating layers of Tensylon and HB25.

As shown in Table 7 for nominal 3.8 psf composite ballistic-resistant panels, the Tensylon UHMWPE tape had a beneficial effect when placed as the strike-face of the ballistic-resistant panel, including a V50 velocity of 2880 fps for the ballistic-resistant panel in which the Tensylon tape comprised the strike-face and 50% of the high modulus component and a V50 velocity of 2897 fps for the ballistic-resistant panel in which the Tensylon tape comprised the strike-face and 25% of the high modulus component.

Table 8 includes ballistic test results for a spall liner for simulated armor with facings of aluminum and High Hardness Steel (HHS) and various backing compositions including various weights of HB25 and various compositions including HB25 and Tensylon tape. All of the armor designs including Tensylon tape as a high modulus component had positive results for rifle threat relative to the requirement.

TABLE 8 Ballistic Data Stmunary - Spall Liner: Total Rifle Threat Frag.** Threat Armor Design AD Relative to Relative to Facing Backing (psf) Rqmt.* (fps) Rqmt. (fps) 1″ 6061 A1/¼″  2.5 psf HB25 27.2 +232 fps Not tested HHS  3.0 psf HB25 27.7 −42 Not tested  3.5 psf HB25 28.2 +419 Not tested 1.25 psf Ten/ 27.2 +152 Not tested 1.25 psf HB25 1.50 psf Ten/ 27.7 +144 Not tested 1.50 psf HB25 1.75 psf Ten/ 28.2 +564 +1000 1.75 psf HB25 1.5″ 6061 A1/¼″ 1.30 psf HB25 33.1 +412 Not tested HHS 1.25 psf Ten/ 33.1 >+464 Not tested 1.25 psf HB25 1.60 psf Ten 33.4 +390 +1639 *Rqmt.—Requirement. **Frag.—Fragmentation

Table 9 includes ballistic test results for a simulated spall liner including the following various configurations: 1) a baseline configuration of ¼″ Ultra High Hard Steel (UHHS) and 1.1 psf of KEVLAR® Reinforced Plastic (KRP), 2) baseline plus 25-mm of HB25 spaced 25-mm behind the KRP, 3) baseline plus 25-mm of high modulus components comprised of 25% Tensylon and 75% HB25 spaced 25-mm behind the KRP, and 4) baseline plus 25-mm of high modulus components comprised of 50% Tensylon and 50% HB25 spaced 25-mm behind the KRP. Test results included the spall cone angle measured at layers 1 and 3 and the average number of fragments that penetrated at layers 1 and 3. The spall cone angle and average number of fragments through for a spall liner including 25% and 50% Tensylon tape were similar to those obtained for a spall liner of 100% HB25.

TABLE 9 Ballistic Data Summary - Simulated Spall Liner, 20 mm FSP: Spall Cone Angle Average # of Fragments (degrees) Through Material Layer 1 Layer 3 Layer 1 Layer 3 Baseline Configuration: 66.44 61.70 214.5 35.0 ¼″ UHHS + 1.1 psf KRP Baseline with: 51.12 35.04 88.50 11.0 25-mm HB25 spaced 25-mm behind KRP Baseline with: 56.46 36.75 89.50 10.5 25-mm 25% Tens/75% HB25 spaced 25-mm behind KRP Baseline with: 52.58 32.57 103.0 9.0 25-mm 50% Tens/50% HB25 spaced 25-mm behind KRP

In another embodiment, ballistic-resistant panels were constructed using Tensylon tape as the high modulus component to determine the effect of molding pressure and temperature on ballistic resistance. Table 10 includes ballistic test results for 2.0 psf panels comprised of cross-plied layers of 1.62-inch width Tensylon UHMWPE tape, with a first series of panels molded at 150 psi and at various temperatures and a second series of panels molded at 500 psi and at various temperatures. The cross-plied layers of Tensylon UHMWPE tape were interleaved with a low density polyolefin scrim (Spunfab PO4605) and pressed and bonded at the various pressures and temperatures recorded in the table. The last entry in Table 10, Tensylon*, was comprised of layers of 1.62-inch Tensylon tape woven into a fabric using a basket weave with the weft arranged at 90° with respect to the warp. The woven layers were pressed with an 18-micron low density polyethylene film to form a 2.2 psf ballistic-resistant panel. The ballistic-resistant panels were tested with 0.30 caliber FSP rounds per MIL-P-46593A and the average V₅₀ velocities recorded.

TABLE 10 Test Results of 2.0 psf Ballistic-resistant panels at Molding Pressures 150 psi and 500 psi and at various Temperatures: High Modulus Molding Temperature Average Component Pressure (psi) (degrees F.) V₅₀ (fps) Tensylon B1 150 200 1601 Tensylon B1 150 210 1702 Tensylon B1 150 220 1630 Tensylon B1 150 230 1689 Tensylon B1 150 240 1611 Tensylon B1 150 250 1634 Tensylon B1 150 260 1577 Tensylon B1 150 270 1543 Tensylon B1 150 280 1551 Tensylon B1 500 180 1790 Tensylon B1 500 190 1717 Tensylon B1 500 200 1692 Tensylon B1 500 210 1647 Tensylon B1 500 220 1588 Tensylon B1 500 230 1593 Tensylon B1 500 240 1566 Tensylon B1 500 250 1649 Tensylon B1 500 260 1703 Tensylon* 500 250 1826 *2.2 psf panel formed of Tensylon 0/90 weave with 1″ tape.

As shown in FIG. 6, the resultant average V₅₀ values for the Tensylon B1 panels of Table 10 were plotted versus temperature and a regression line fitted each series of data points. The ballistic resistance of the panels generally increased as the molding temperature was decreased.

As shown in FIG. 5 the invention is a ballistic-resistant panel comprising a compressed stack of interleaved layers 70, 72, 74, 76 of high modulus material wherein the high modulus material includes a modulus greater than 1,000 grams per denier. A first portion 70, 72 of the interleaved layers of high modulus material include a plurality of interleaved layers consisting of non-fibrous ultra high molecular weight polyethylene tape 64. A second portion of the interleaved layers of high modulus material include a plurality of interleaved layers 74, 76 consisting of cross-plied fibers embedded in resin. As shown in FIGS. 3 and 4, an adhesive 68 is included on each of the interleaved layers 70, 72 of non-fibrous ultra high molecular weight polyethylene tape. The first portion 70, 72 of the interleaved layers form the strike-face of the ballistic-resistant panel.

With reference to FIGS. 3 and 4, each of the layers of non-fibrous ultra high molecular weight polyethylene tape in the ballistic-resistant panel includes a plurality of tape strips 64. The tape strips 64 include a width of at least 1.0 inch, the tape strips include edges, and the tape strips 64 are fused together in a butt joint or overlap joint 66 at the edges or woven into a fabric.

In a ballistic-resistant panel according to the present invention, the non-fibrous ultra high molecular weight polyethylene tape includes a viscosity-average molecular weight of at least 2,000,000, a thickness of between 0.0015 and 0.004 inch, and a modulus of greater than 1400 grams per denier. The tape 64 in each of the interleaved layers 60, 62 of non-fibrous ultra high molecular weight polyethylene tape is unidirectional and the direction of orientation of the tape in each of the interleaved layers of non-fibrous ultra high molecular weight polyethylene tape is at an angle of at least 30 degrees with respect to the direction of orientation of the tape in an adjacent layer of the tape. In the ballistic-resistant panel, the compressed stack of interleaved layers of high modulus material are compressed and bonded together at a pressure of between 100 and 4,000 psi and a temperature of between 150 and 300 degrees F.

In a ballistic-resistant panel according to the present invention, the adhesive 68 on each of the interleaved layers of the non-fibrous ultra high molecular weight polyethylene tape is selected from the group consisting of polyamide, polyolefin, ethylene vinylacetate copolymer, polyurethane, ethylene acrylic acid copolymer, polystryrene-isoprene copolymer, or ethylene/methacrylic acid copolymer. The adhesive comprises between 5.7 and 10.4 weight percent of the total weight of the panel. The adhesive can consist of a scrim or film of adhesive on each of the interleaved layers of non-fibrous UHMWPE tape. Alternatively, the adhesive may be in the form of a liquid dispersion applied to one side of the non-fibrous UHMWPE tapes.

The non-fibrous UHMWPE tape strips are formed from stretching partially oriented UHMWPE tape to a total draw ratio of 100:1 or greater wherein the draw ratio is defined as the length after stretching divided by the length before stretching. The tape strips include a width to thickness ratio of at least 400:1 and a denier of 6,000 or greater.

Referring to FIGS. 3 and 4, another embodiment of the ballistic-resistant panel is comprised of a plurality of interleaved layers 60, 62 consisting of non-fibrous ultra high molecular weight polyethylene tape 64. Each of the layers of non-fibrous ultra high molecular weight polyethylene tape 64 include a plurality of monolithic tape strips joined together in a sheet structure 60, 62 including joints 66 between adjoining strips 64 wherein the joints 66 include an intermingling of molecules between the molecules of the adjoining strips 64 and a higher strength in the joints 66 than in the adjoining strips 64 and each of the tape strips 64 include a modulus of greater than 1400 grams per denier. The plurality of tape strips 64 in each of the layers including a first portion 60 of tape strips oriented at a first angle and a second portion 62 of tape strips oriented at substantially 90 degrees with respect to the first angle. The plurality of interleaved layers of non-fibrous ultra high molecular weight polyethylene tape 64 are bonded together by heat and pressure. The heat of bonding is at least 150 degrees F. and the pressure of bonding is at least 150 psi. The first portion of tape strips in the layer includes a first ply of tape strips arranged side to side in a butt joint and bonded together by heat and pressure. The second portion of tape strips in the layer includes a second ply of tape strips arranged side to side in a butt joint and bonded together by heat and pressure. The first portion of tape strips and the second portion of tape strips are bonded together to form a cross-plied layer.

With reference to Table 8, a ballistic-resistant article comprising a metallic strike face (see “Facing” column in Table 8, p. 19) and a plurality of interleaved layers of polymeric material (see “Backing” column in Table 8, p. 19) stacked against the strike face, the plurality of interleaved layers being comprised consisting of a multilayer sheet of first and second layers (p. 19, Table 8, see rows 4-6 of “Backing”), wherein at least some of the first layers comprise consist of drawn polymeric fibers (p. 19, Table 8, 1.25-1.75 psf HB25) and wherein at least some of the second layers comprise consist of drawn polymeric tapes (p. 19, Table 8, 1.25-1.75 psf Ten).

Although the embodiments of ballistic-resistant panels describe above were prepared at specific parameters, other variations of processing conditions are possible without departing from the scope of the invention. For example, although the Tensylon UHMWPE tape in adjacent layers of the ballistic-resistant panel were oriented at 0° and 90° respectively, other orientations are possible, such as 0° and 45° in adjacent layers, or 0°, 45°, −4D and 90° for each three successive layers. Preferably the direction of orientation of the tape in each of the interleaved layers of non-fibrous ultra high molecular weight polyethylene tape is at an angle of at least 30 degrees with respect to the direction of orientation of the tape in an adjacent layer. Although the specific molding temperatures tested herein were between 180 and 280° F., it is believed that molding temperatures between 150° F. and 300° F. are acceptable for forming a ballistic-resistant panel according to the present invention. Although specific molding pressures of 150, 500, and 3000 psi were tested, it is believed that molding pressures between 100 and 4000 psi are acceptable for forming ballistic-resistant panels according to the present invention.

Although in one embodiment herein the Tensylon tape was woven into a fabric using a basket weave, it is within the scope of the present invention to form the Tensylon tape into fabric using any fabric weave, such as plain weave, twill weave, satin weave, and the like.

Having thus described the invention with reference to a preferred embodiment, it is to be understood that the invention is not so limited by the description herein but is defined as follows by the appended claims. 

1. A ballistic-resistant panel comprising: a compressed stack of interleaved layers of high modulus material wherein said high modulus material includes a modulus greater than 1,000 grams per denier; a first portion of said interleaved layers of high modulus material including a plurality of interleaved layers consisting of non-fibrous ultra high molecular weight polyethylene (UHMWPE) tape; a second portion of said interleaved layers of high modulus material including a plurality of interleaved layers consisting of cross-plied fibers embedded in resin; and an adhesive on each of said interleaved layers of said non-fibrous ultra high molecular weight polyethylene tape.
 2. The ballistic-resistant panel of claim 1 wherein each of said layers of non-fibrous ultra high molecular weight polyethylene tape includes a plurality of tape strips; said tape strips including a width of at least 1.0 inch; said tape strips include edges; and said tape strips are fused together in a butt joint or overlap joint at said edges or woven into a fabric.
 3. The ballistic-resistant panel of claim 1 wherein said non-fibrous ultra high molecular weight polyethylene tape includes a viscosity-average molecular weight of at least 2,000,000; a thickness of between 0.0015 and 0.004 inch; and a modulus of greater than 1400 grams per denier.
 4. The ballistic-resistant panel of claim 1 wherein said tape in each of said interleaved layers of non-fibrous ultra high molecular weight polyethylene tape is unidirectional; and the direction of orientation of said tape in each of said interleaved layers of non-fibrous ultra high molecular weight polyethylene tape is at an angle of at least 30 degrees with respect to the direction of orientation of said tape in an adjacent layer of said tape.
 5. The ballistic-resistant panel of claim 1 wherein said compressed stack of interleaved layers of high modulus material are compressed and bonded together at a pressure of between 100 and 4,000 psi; and a temperature of between 150 and 300 degrees F.
 6. The ballistic-resistant panel of claim 1 wherein said adhesive on each of said interleaved layers of said non-fibrous ultra high molecular weight polyethylene tape is selected from the group consisting of polyamide, polyolefin, ethylene vinylacetate copolymer, polyurethane, ethylene acrylic acid copolymer, polystryrene-isoprene copolymer, or ethylene/methacrylic acid copolymer.
 7. The ballistic-resistant panel of claim 1 wherein said adhesive comprises between 5.7 and 10.4 weight percent of the total weight of said panel.
 8. The ballistic-resistant panel of claim 2 wherein said non-fibrous UHMWPE tape strips are formed from stretching partially oriented UHMWPE tape to a total draw ratio of 100:1 or greater wherein the draw ratio is defined as the length after stretching divided by the length before stretching; said tape strips include a width to thickness ratio of at least 400:1; and said tape strips include a denier of 6,000 or greater.
 9. The ballistic-resistant panel of claim 1 wherein said adhesive includes a scrim or film of adhesive on each of said interleaved layers of non-fibrous UHMWPE tape.
 10. The ballistic-resistant panel of claim 1 wherein each of said interleaved layers of said non-fibrous UHMWPE tape includes two sides; and said adhesive is in the form of a liquid dispersion applied to one of said non-fibrous UHMWPE tape.
 11. The ballistic-resistant panel of claim 1 wherein said first portion of said interleaved layers form the strike-face of said ballistic-resistant panel.
 12. A ballistic-resistant panel comprising: a plurality of interleaved layers consisting of non-fibrous ultra high molecular weight polyethylene tape; each of said layers of non-fibrous ultra high molecular weight polyethylene tape including a plurality of monolithic tape strips joined together in a sheet structure including joints between adjoining strips wherein said joints include an intermingling of molecules between said molecules of said adjoining strips and a higher strength in said joints than in said adjoining strips and each of said tape strips including a modulus of greater than 1400 grams per denier; said plurality of tape strips in each of said layers including a first portion of tape strips oriented at a first angle and a second portion of tape strips oriented at substantially 90 degrees with respect to said first angle; and said plurality of interleaved layers of non-fibrous ultra high molecular weight polyethylene tape bonded together by heat and pressure.
 13. The ballistic-resistant panel of claim 12 wherein said heat of bonding is at least 150 degrees F. and said pressure of bonding is at least 150 psi.
 14. The ballistic-resistant panel of claim 12 wherein said first portion of tape strips in said layer includes a first ply of tape strips arranged side to side in a butt joint and bonded together by heat and pressure; said second portion of tape strips in said layer includes a second ply of tape strips arranged side to side in a butt joint and bonded together by heat and pressure; and said first portion of tape strips and said second portion of tape strips are bonded together to form a cross-plied layer.
 15. A ballistic-resistant article comprising a metallic strike face and a plurality of interleaved layers of polymeric material stacked against the strike face, the plurality of interleaved layers consisting of a multilayer sheet of first and second layers, wherein at least some of the first layers consist of drawn polymeric fibers and wherein at least some of the second layers consist of drawn polymeric tapes. 